Shaft bearing surface



Patented Sept. 18, 1962 ice This invention relates to a method ofapplying a metallic bearing surface to the surface of a member made of adifferent metal or alloy.

A simplified flow diagram of the method of the present invention is asfollows:

Shaft of nickel base alloy Masking of areas except where bearing surfacerequired Spraying with bearing metal Immersion into bath of boriccryolite at high temperature Maintaining in bath until temperature ofshaft reaches that of bath Removal from bath According to the inventiona method of applying, to a first metallic surface, a bearing surface ofa second metal or alloy, comprises spraying the second metal or alloy onthe first surface and then immersing the sprayed area into a fusingbath. The bath can be, for example, molten boric cryolite, or bariumchloride.

Preferably the bath is raised to a suitable temperature, say 1060 to1070 C., prior to insertion of the sprayed area into the bath, and thesprayed area is retained in the bath until the metal member has reachedthe temperature of the bath.

This process causes diffusion of the second metal or alloy to a limitedextent into the first metallic surface. For example, in the use of Metco16C alloy as a bearing surface metal for application to Nimonic 80A, theMetco 16C diffuses to a depth of about five thousandths of an inch intothe Nimonic alloy.

The Metco 16C is then firmly keyed to the Nimonic 80A and a fulldiffusion bond is established.

One particular application of the invention is to the production ofjournal shafts for supporting thrust reversers of gas turbine engines.These shafts have to be made of an alloy which will withstand the hightemperatures and rapid changes of temperature involved in gas turbinereverser operation. Nimonic 80A is one such metal which is suitable, butthis metal is not suitable itself for use :as a bearing surface. Asunderstood in the art, Nimonic 80A is an alloy having a composition of18% to 21% chromium, 5.0% maximum iron, 1.8% to 2.7% titanium, 0.5% to1.8% aluminum, 2.0% maximum cobalt, 1.0% maximum manganese, 1.0% maximumsilicon, 0.1% maximum carbon and a balance of nickel.

Metco 16C, which is an alloy comprising nickel as its main constituentwith about 16% of chromium and additions of boron, silicon, copper andiron is a suitable alloy for forming a bearing surface. As understood inthe art Metco 16C is an alloy having a composition of 16.0% chromium,4.0% boron, 4.0% silicon, 3.0% copper, 2.5% iron, 3.0% molybdenum, 0.5%carbon and a balance of nickel.

The difficulty lies in bonding the Metco 16C to the Nimonic A and it isthe purpose of this invention to overcome the difliculty.

The method used in practice is to mask the portion of the Nimonic alloyshaft which is not to be sprayed and prepare it by blasting with sand orwith steel shot the area which is to be sprayed. The bearing area isthen sprayed With the bearing metal. A bath of boric cryolite is thenraised to a temperature of 1060 to 1070 C., the shaft is inserted intothe bath so that the sprayed part is entirely immersed and it is leftthere until the temperature of the shaft reaches that of the bath. Thisusually takes about 10 to 20 minutes, by which time the Metco 16C isdiffused into the Nimonic alloy to a sufiicient depth to make a fulldiffusion bond.

Other heat resistant materials which can be used in place of Metco 16Cin this particular application include Stellite and like materials. Asunderstood in the art Stellite is an alloy having a composition of 40%to 60% cobalt, 20% to 35% chromium, 0 to 25% tungsten, .75 to 2.5%carbon and O to 3% silicon.

The preparation of the boric cryolite flux bath for a different purposeis described in our British Patent 698,425 and the bath may be preparedin the same way for this application.

What I claim is:

1. -A method of applying a hard metal bearing surface to a shaft made ofnickel base high temperature alloy comprising the steps of: masking thearea of the shaft except Where the hard metal bearing surface is to beapplied, sand blasting the unmasked area, spraying the unmasked areawith the hard bearing metal, entirely im mersing the sprayed part of theshaft into a bath of boric cryolite at a high temperature, maintainingthe immersed portion in the bath until the temperature of the shaftreaches about that of the bath, whereby the hard bearing metal isdiffused into the nickel base high temperature alloy of the shaft to asufficient depth to make a full diffusion bond, and then removing theshaft from the bath.

2. A method in accordance with claim 1 wherein the temperature of thebath is elevated in the order of 1060 C. to 1070" C.

3. A method in accordance with claim 11 wherein the hard bearing metalis a hard alloy comprising nickel as its main constituent with about 16%of chromium and additions of boron, silicon, copper and iron.

References Cited in the file of this patent UNITED STATES PATENTS2,315,725 Moller Apr. 6, 1943 2,588,421 Shepard Mar. 11, 1952 2,885,304Thomson et a1. May 5, 1959 2,889,238 Long et al. June 2, 1959 2,955,958Brown Oct. 11, 1960

1. A METHOD OF APPLYING A HARD METAL BEARING SURFACE TO A SHAFT MADE OFNICKEL BASE HIGH TEMPERATURE ALLOY COMPRISING THE STEPS OF: MASKING THEAREA OF THE SHAFT EXCEPT WHERE THE HARD METAL BEARING SURFACE IS TO BEAPPLIED, SAND BLASTING THE UNMASKED AREA, SPRAYING THE UNMASKED AREAWITH THE HARD BEARING METAL, ENTIRELY IMMERSING THE SPRAYED PART OF THESHAFT INTO A BATH OF BORIC CRYOLITE AT A HIGH TEMPERATURE, MAINTAININGTHE IMMERSED PORTION IN THE BATH UNTIL THE TEMPERATURE OF THE SHAFTREACHES ABOUT THAT OF THE BATH, WHEREBY THE HARD BEARING METAL ISDIFFUSED INTO THE NICKEL BASE HIGH TEMPERATURE ALLOY OF THE SHAFT TO ASUFFICIENT DEPTH TO MAKE A FULL DIFFUSION BOND, AND THEN REMOVING THESHAFT FROM THE BATH